Understanding the basic cell biology of the corneal epithelium in disease or injury is important in learning how to clinically treat corneal diseases or injuries. We will study two basic cellular processes in the corneal epithelium by techniques of electron and fluorescence microscopy, and cytochemistry. They are: (1) the lysosome system in the corneal epithelium and how it relates to disease processes, and (2) the cytoplasmic machinery within corneal epithelial cells responsible for movement of the cells across abrasions and wounds. During previous grant years we found that in the rat model of the human disease, tyrosinosis, crystals form in cells of early focal lesions. As the crystals grow they pierce and disrupt cell organelles and cells. We demonstrated that some crystals are packaged within lysosomes and that a great increase in lysosomes occurs in cells of focal lesions that develop 60 hours after rats are placed on high tyrosine diets. These studies demonstrate where and in what time frame lysosomal enzymes can be produced or activated in the corneal epithelium. During the next grant year we hope to determine if this increase in lysosomal enzymes is unique to the model of tyrosine keratopathy or whether it is a common feature in other epithelial disorders which lead to ulceration and neovascularization. An observation made during early studies of the rat model of tyrosinosis, was that cells moving to cover corneal ulcers caused by high tyrosine, contained bundles of cytoplasm filaments. Subsequent studies have demonstrated that the filaments are actin filaments, and that proparacaine, a commonly used ophthalmologic local anesthetic, and cytochalasin B, can disrupt these filaments and retard wound healing. We plan additional studies of factors stimulating and inhibiting formation or function of the actin filament system as it functions to move epithelial cells across corneal abrasions and wounds.